Functionalized copolyimide membranes for the separation of gaseous and liquid mixtures

Abstract

SummaryFunctionalized copolyimides continue to attract much attention as membrane materials because they can fulfill the demands for industrial applications. Thus not only good separation characteristics but also high temperature stability and chemical resistance are required. Furthermore, it is very important that membrane materials are resistant to plasticization since it has been shown that this phenomenon leads to a significant increase in permeability with a dramatic loss in selectivity. Plasticization effects occur with most polymer membranes at high CO2 concentrations and pressures, respectively. Plasticization effects are also observed with higher hydrocarbons such as propylene, propane, aromatics or sulfur containing aromatics. Unfortunately, these components are present in mixtures of high commercial relevance and can be separated economically by single membrane units or hybrid processes where conventional separation units are combined with membrane-based processes. In this paper the advantages of carboxy group containing 6FDA (4,4′-hexafluoroisopropylidene diphthalic anhydride) -copolyimides are discussed based on the experimental results for non cross-linked, ionically and covalently cross-linked membrane materials with respect to the separation of olefins/paraffins, e.g. propylene/propane, aromatic/aliphatic separation e.g. benzene/cyclohexane as well as high pressure gas separations, e.g. CO2/CH4 mixtures. In addition, opportunities for implementing the membrane units in conventional separation processes are discussed.

Investigation of Cross-Linked and Additive Containing Polymer Materials for Membranes with Improved Performance in Pervaporation and Gas Separation

“…Permeate pressure was kept between 20 and 25 bar [9]; ( b ) CO 2 /CH 4 separation characteristics for the 6FDA-6FpDA/6FDA-4MPD/6FDA-DABA 3:1:1 copolyimide ionically crosslinked with aluminium(III)-acetylacetonate (blue) and covalently crosslinked with ethylene glycol (orange) at 35 °C using a 50:50 CO 2 /CH 4 feed gas mixture [9]. …”

“…The permeability is a measure of the permeate's quantity while the selectivity describes its quality (mole fraction of preferentially permeating component in the permeate) [9]. …”

Separation of phenanthrene/N‐tetradecane mixtures (model diesel) via pervaporation using an aromatic polyimide membrane

“…Earlier authors have studied the effect of membrane pretreatment on pervaporative separation with various crosslinked copolyimide membranes. Generally, membrane pretreatment is an appropriate method of enhancing J for different systems at any corresponding temperature . The effect of pretreatment on β is not generally well explained in literature .…”

Separation of polyaromatic hydrocarbons from model diesel composition via pervaporation using a fabricated aromatic polyimide membrane and process optimization

“…The percent sorption was calculated using the following equation : where M s and M d are the mass of the swollen membrane and that of the dried membrane, respectively.…”

“…Membrane based separation technology has emerged as a promising alternative in situations, where conventional processes are ineffective . Currently, the worldwide membrane market has a steady growth of 10–15% each year . The separation is performed by simple, physical means without chemically altering the components.…”